Why do some zygopterans (Odonata) perch with open wings?


Zygoptera show two perching modes, one with wings closed and one with wings open. These perching modes are distributed unequally through the suborder; most Zygoptera perch with closed wings, but species in 43 genera of eight families at least occasionally – in most cases usually – perch with open wings. Alternative hypotheses to explain this dichotomy are assessed. The dichotomy does not seem to be explicable by the Phylogenetic Inertia Hypothesis (PIH), the Wing Display Hypothesis (WDH), or the Thermoregulation Hypothesis (TH). I propose a hypothesis that the openwing position used by some zygopterans facilitates either more rapid takeoff or quicker orientation toward flying prey: the Quick Takeoff Hypothesis (QTH). That openwing species usually take flying prey furnishes support for the QTH, although many closedwing species also take flying prey. However, as most zygopterans perch with closed wings, that behavior needs explanation too, and I propose a hypothesis that perching with wings spread may make a zygopteran more conspicuous to predators and thus may be disadvantageous: the Shiny Wing Hypothesis (SWH). Larger species are less at risk of predation than smaller species, open wings in shade should be less conspicuous than in sunlight, and the majority of zygopterans with open wings are large tropical shade perchers, furnishing support for the SWH.

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